蒋晟(JIANG,Sheng), a Microsoft MVP @Austin, Texas

In Visual C# 2005 SP1, I added an object data source to a web page that uses my business class as the select method. The method has one parameter of type Guid. The data source wizard generates code like this

<asp:Parameter DbType="Guid" Name="rowId" />

Although the web server has .Net 2.0 SP1 installed (I checked the registry), it still throws an error

Type 'System.Web.UI.WebControls.Parameter' does not have a public property named 'DbType'

The walk around is easy:

<asp:Parameter Type="Object" Name="rowId" />

To use Microsoft Office Live, your computer must meet one of the following requirements:

Microsoft Internet Explorer 6 or 7, running on Microsoft Windows XP, Windows Server 2003 or Windows Vista. You can download Internet Explorer from the Windows Internet Explorer page.
Mozilla Firefox running on Windows XP, Windows Server 2003, Windows Vista, or Mac OS X 10.2.x and later. You can download Firefox from the Firefox download page.

Looks like the Microsoft Award for Customer Excellence award I got a few years ago...

Visual C++项目组今天发布了Visual C++ 2008 Feature Pack。这个Feature Pack包含了一些以前需要付费给BCG Soft才可以使用的控件，例如BCG著名的窗口布局和风格自定义功能，不过也有一些有用的控件，例如文件夹列表、文件夹树、属性窗格等等。

这个Feature Pack也包含从Dinkumware获得授权的一些对STL的扩展，实现了TR1草案。这包含新的随机算法、集合类和正则表达式支持。关于TR1的更多信息，可以参考Dinkumware的网站。

安装了这个Feature Pack之后，生成的应用程序在发布时需要同时发布新版本的MFC和CRT组件。预计对这个Feature Pack的技术支持策略会和VC6中从Dinkumware获得授权的STL库会是一个级别，也就是说，BCG Soft、Dinkumware和微软都会提供技术支持。如果在安装了这个Feature Pack之后需要安装Windows SDK 6.1，那么在安装完SDK之后需要修复Visual Studio 2008以保持文件是最新的。

目前发布的这个补丁只支持英文版的Visual Studio 2008 标准版或更高版本，其他语言版的Visual Studio 2008 要获得这些新的功能的话，需要等到Visual Studio 2008 SP1发布。Visual Studio 2008会包含这个Feature Pack。

A C# program for those who don't know MSI SDK or C++. C++ programmers can find the API inside the msi.h  file in Windows SDK.

class Program
{
    static int Main(string[] args)
    {
        uint pathSize = 0;
        try
        {
            foreach (string componentId in args)
            {
                MsiInstallState state = MsiLocateComponent(
                    componentId, null, ref pathSize);
                if (state != MsiInstallState.Local)
                {
                    return ERROR_UNKNOWN_COMPONENT;
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
            Console.WriteLine(ex.StackTrace);
            return ERROR_MOD_NOT_FOUND;
        }
        return 0;
    }
    [DllImport("msi.dll", CharSet = CharSet.Auto)]
    extern static internal MsiInstallState MsiLocateComponent(string component, string path, ref uint pathSize);
    /// <summary>Enumeration of MSI install states.</summary>
    internal enum MsiInstallState : int
    {
        Local = 3
    }
    const int ERROR_MOD_NOT_FOUND = 126;
    const int ERROR_UNKNOWN_COMPONENT = 1607;
}

The first 3 Dell support technicians tried to persuade me to clean the temp files, to remove unnecessary startup programs and to reinstall Windows. It does not help if the computer complains an error during self test. I keep saying a self test error can not be solved by twisting the OS, but they won't listen. After educating the representatives for a week I finally got one that has better experience (and better English) to examine my computer. A full system test shows bad sectors on the hard drive, and totally toasted the hard drive. Luckily I just bought the computer for 6 months so I asked for a replacement. Dell sent me one in 2 days and I sent back the broken one.

Now my back up hard drive started to fail ... Time to call Seagate.

一个面向Visual C++ 2008的MFC更新测试版已经发布，同时也提供了文档的下载。这个版本包含新的界面的特性，例如Office Ribbon、2003和XP风格,Visual Studio风格和MDI标签。另外，这个版本也包含部分TR1的实现，例如正则表达式、更加丰富的集合和智能指针。

另外，在下载页面居然说这个版本还不支持Visual Studio 2008 Service Pack 1的Beta版，正式版才出来几天SP1的测试版就出来了？

Download the code for this article (22KB)

.Net 2.0 introduced autocompletion in TextBox and ComboBox. It is obvious that autocomplete is not very useful when the number of options is small. However, when your option becomes too many, pre-filling of all options to an AutoCompleteStringCollection becomes impractical, especially when your data comes from a remote computer. An alternative is to replace the AutoCompleteCustomSource in a TextChanged event, however, users are getting random AccessViolationException when trying to replace it.  In this article I will demonstrate another alternative, using a BindingSource as the data source of options and bypassing the .Net framework and call the underline Windows API directly.

The first thing I need to do is to port the APIs to managed code. The autocompletion API is exposed as a COM object, so I need to write managed version of its interfaces:

    [ComImport]
    [InterfaceType(ComInterfaceType::InterfaceIsIUnknown)]
    [Guid("EAC04BC0-3791-11D2-BB95-0060977B464C")]
    [SuppressUnmanagedCodeSecurity]
    interface  class IAutoComplete2
    {
             [PreserveSig] int Init(
            HandleRef hwndEdit,
            IEnumString^ punkACL,
             String^ pwszRegKeyPath,           
            String^ pwszQuickComplete
        );
        void Enable( [MarshalAs(UnmanagedType::Bool)] bool value);

        int SetOptions(int dwFlag);

        void GetOptions([Out]IntPtr pdwFlag);
    };
Second, I need to create the autocomplete object and query the IAutoComplete2 interface:

       Type^ autoCompleteType = Type::GetTypeFromCLSID(CLSID_AutoComplete);
        try{
            autoComplete2 =(IAutoComplete2^)(Activator::CreateInstance(autoCompleteType));
        }
        catch(Exception^ e)
        {
            Marshal::ReleaseComObject(autoComplete2);
            autoComplete2 = nullptr;
        }

Third, I need to bind it to an TextBox control:

    bool AutocompleteBindingSource::Bind()
    {
        if (nullptr==this->autoComplete2)
            return false;
        try
        {
            this->autoComplete2->SetOptions((int)ControlToBind->AutoCompleteMode);
            this->autoComplete2->Init(
                HandleRef(ControlToBind,ControlToBind->Handle),
                this,
                String::Empty
                ,String::Empty);
            return true;
        }
        catch(Exception^e)
        {
            return false;
        }

    }

Finally, I need to implement IEnumString to provide a list of options. Luckily, .Net has declared this interface, so I don't need to port it to managed code, however, I still need to write my binding code in my implementation of IEnumString.

    void AutocompleteBindingSource::Reset()
    {
        this->current = 0;
        if(BindingSource!=nullptr)
            this->size=BindingSource->Count;
    }

        int AutocompleteBindingSource::Next(
        int celt, [Out, MarshalAs(UnmanagedType::LPArray, ArraySubType=UnmanagedType::LPWStr, SizeParamIndex=0)] array<String^>^ rgelt, IntPtr pceltFetched)
    {
        if (celt < 0)        {
            return E_INVALIDARG;
        }
        int index = 0;
        while ((this->current < this->size) && (celt > 0))
        {
            Object^ item=this->BindingSource->default[this->current];

            bool useDisplayMember=false;

            if(!String::IsNullOrEmpty(DisplayMember))
            {
                ICustomTypeDescriptor^ customTypeDescriptor=dynamic_cast<ICustomTypeDescriptor^>(item);
                if(customTypeDescriptor!=nullptr)
                {
                    PropertyDescriptorCollection^ propertyDescriptorCollection=
                        customTypeDescriptor->GetProperties();
                    if(propertyDescriptorCollection!=nullptr)
                    {
                        PropertyDescriptor^ propertyDescriptor=propertyDescriptorCollection->default[DisplayMember];
                        if(propertyDescriptor!=nullptr)
                        {
                            rgelt[index] = propertyDescriptor->GetValue(item)->ToString();
                            useDisplayMember=true;
                        }
                    }
                }
            }

            if(!useDisplayMember)
            {
                if(item!=nullptr)
                {
                    rgelt[index] = item->ToString();
                }
            }
            this->current++;
            index++;
            celt--;
        }
        if ((pceltFetched != IntPtr::Zero))
        {
            Marshal::WriteInt32(pceltFetched, index);
        }
        if ((celt != 0))
        {
            return 1;
        }
        return 0;

    }

Here the DisplayMember property is the name of the property in the data source to be displayed. If the property specified by the value of the DataMember property does not exist, I use ToString to get a text representation of the current item in the data source.

You may want to ask, where is the filtering code? Well, that is implemented by BindingSource class.

       System::Void FormTest::textBoxDemo_TextChanged(System::Object^  sender, System::EventArgs^  e)
    {
        static bool inThisFunction=false;
        if(!inThisFunction)
        {
            inThisFunction=true;
            if(String::IsNullOrEmpty(textBoxDemo->Text))
                bindingSourceAutoComplete->Filter=nullptr;
            else
            {
                System::String^ addText=textBoxDemo->Text+"og/NextElement";
                dataSetDemo->Tables[0]->DefaultView->Sort="Text";
                if(dataSetDemo->Tables[0]->DefaultView->FindRows(addText)->Length==0)
                {
                    System::Data::DataRow^ row=dataSetDemo->Tables[0]->NewRow();
                    row->default[0]=addText;
                    dataSetDemo->Tables[0]->Rows->Add(row);
                }
                bindingSourceAutoComplete->Filter=
                    String::Format("{0} LIKE '{1}%'"
                    ,dataSetDemo->Tables[0]->Columns[0]->Caption
                    ,textBoxDemo->Text);
            }
            if(textBoxDemo->SelectionStart>0)
            {
                autocompleteBindingSource1->Reset();
                autocompleteBindingSource1->Bind();
                String^ text=textBoxDemo->Text;
                int selectionStart=textBoxDemo->SelectionStart;
                int selectionLength=textBoxDemo->SelectionLength;
                textBoxDemo->SelectionStart=0;
                textBoxDemo->SelectionLength=0;
                textBoxDemo->SelectAll();            
                System::Windows::Forms::SendKeys::SendWait("{BACKSPACE}");
                textBoxDemo->Text=text;
                textBoxDemo->SelectionStart=selectionStart-1;
                textBoxDemo->SelectionLength=selectionLength+1;
                System::Windows::Forms::SendKeys::SendWait(textBoxDemo->SelectedText);
            }
            inThisFunction=false;
        }
    }

Somehow Windows caches the result. If I don't clear the text, my IEnumString implementation won't be asked again for candidate strings (pointed out by Andy Gilman). 

The BindingSource class checks the data source to see if they support the IBindingListView. If IBindingListView is supported, the BindingSource class delegates sorting and filtering to the data source.  In this sample, the data source of the BindingSource object is a DataSet, and the DataMember of BindingSource object is the name of the first table , so BindingSource creates a DataView as its data source. The DataView class implements IBindingListView and filters its data using expressions parsed from the filter string. In reality, the data source could be a business object that implements IBindingListView and supports filtering and sorting with stored procedures.

This sample does not consider compound autocomplete object support. If you want to get your options from multiple sources, you need to use IObjMgr to add sources to the autocomplete object.

Reference

• Using Autocomplete
• BindingSource Component Architecture